1. Field of the Invention
The present invention relates to a projection type display device such as a liquid crystal projector.
2. Description of the Related Art
A liquid crystal projector conventionally includes a light source supported by a reflector; and a light bulb composed of a liquid crystal panel for modulating illumination light emitted from the light source based on an input video signal, etc. The modulated illumination light is projected onto a screen or the like through a projection lens.
In such a liquid crystal projector, various optical components whose temperatures are elevated when the liquid crystal projector is driven, for example, a light bulb, a polarizing plate and the like are required to be cooled by cooling air so as to keep their temperatures so as not to exceed a maximum guaranteed temperature. Moreover, it is necessary to exhaust heat generated from a light source or a power source to the exterior of the device so as to prevent a temperature of the device from increasing.
On the other hand, in the liquid crystal projector, for example, if a sirocco fan or an axial fan is used, the fan makes noise. The noise is required to be restrained as much as possible.
Various techniques for realizing both the effective cooling of a device and the restriction of noise generation have been conventionally proposed (see Japanese Patent Application Laid Open JP 2001-51349 A).
An outlet (exhaust louver) for exhausting air from a box of a liquid crystal projector is often provided on a lateral face of the box. With the exhaust louver provided on the lateral face of the box, noise generated in the box is likely to be diffused through the exhaust louver. Moreover, there is a possibility that the exhaust louver may act as a resistance against airflow to elevate a noise level.
Moreover, FIG. 13 shows an example of a liquid crystal projector. A liquid crystal projector 1 shown in FIG. 13 includes: an optical unit frame 10 placed in a box 2; and a projection lens 11 placed so as to be continuous with the optical unit frame 10. Optical paths, through which, for example, red light, blue light and green light respectively pass, are provided in the optical unit frame 10. Taking green light as an example, green light propagating through the optical path passes through a condenser lens 12, an incident-side polarizing plate 13, a liquid crystal panel 14 and an output-side polarizing plate 15, which are provided in the optical path, to reach a cross prism 16.
The green light, which is condensed by the condenser lens 12 to be incident on the liquid crystal panel 14 through the polarizing plate 13, is modulated on the liquid crystal panel 14 based on image data. Then, the modulated green light passes through the polarizing plate 15 to control its transmittance.
The green light having the controlled transmittance is coupled with red light and blue light, each obtaining a controlled transmittance in a similar manner, at the cross prism 16.
The resulting light coupled at the cross prism 16 is projected onto a screen (not shown) through the projection lens 11 to display an image thereon.
In such a liquid crystal projector, optical components that generate heat due to energy of the emitted light, such as the polarizing plates 13 and 15 and the liquid crystal panel 14, are cooled with air blown by a sirocco fan 40.
For example, the sirocco fan 40 placed in a lower part of the box 2 takes air in from an air inlet port 20 to blow the intake air through an air blowing port 21, thereby cooling the optical components.
Conventionally, as shown in FIG. 13, air blown from the air blowing port 21 is guided toward the optical components such as the liquid crystal panel through a duct 30 connected to the air blowing port 21 while changing a direction of the airflow with an inclined plane 31 of the duct 30 (for example, see Japanese Patent Application Laid Open JP 2002-189250 A (FIG. 4), Japanese Patent Application Laid Open JP 2002-189251 A (FIG. 2) and Japanese Patent Application Laid Open JP 2001-13589 A (FIG. 2)).
The airflow whose direction has been changed by the inclined plane 31 is sent to the heat-generating optical components through an inlet-side opening 22 provided for an optical unit frame 10 so as to be exhausted from an exhaust-side opening 23, thereby cooling the optical components.
Another liquid crystal projector, in which the sirocco fan 40 is placed along its lateral face instead of being placed in a lower part of the box 2, is also known (for example, Japanese Patent Application Laid Open JP 2002-188597 A (FIG. 2)).
Also in this case, air blown from the sirocco fan 40 is similarly guided to the optical components that generate heat, via a duct connected to the air blowing port of the sirocco fan 40.